Coffee can do a body good; we’ve said it on this website before, in stories about the health benefits about your morning cup of Joe. But too much of it could be bad for your waistline.

A new study found mice that downed a high-fat diet with a large amount of chlorogenic acid (CGA, an antioxidant found in coffee) over a 12-week period stored more fat and experienced insulin resistance, a precursor to type 2 diabetes.

These results were unexpected. “Our hypothesis was that the coffee compound would reduce weight gain and improve insulin sensitivity,” says Kevin D. Croft, Ph.D., of the University of Western Australia School of Medicine and Pharmacology and study co-author. “Clearly this is not the case.”

Don’t break into pre-coffee jitters just yet. The mice in the study had doses of CGA equivalent to five or six cups of coffee per day. Previous research has shown CGA in moderation can reduce blood pressure, increase insulin resistance and prevent weight gain.

If you limit yourself to three or four eight-ounce cups (or fewer) of coffee a day, you should be fine, Croft says.